The present invention relates to an expansion valve for controlling the flow rate of the refrigerant equipped to the refrigeration cycle of an air conditioning device for a vehicle and the like.
A known expansion valve comprises a prism-shaped valve body, the body being equipped with a valve chamber and a power element for operating a valve means formed within the valve chamber.
This kind of expansion valve comprises two passages communicated to the valve chamber, and a passage through which the refrigerant returning from the evaporator to the compressor travels. An operating shaft capable of communicating the movement of the power element to the valve means penetrates the passage through which the refrigerant returning from the evaporator to the compressor travels, and transmits the temperature information of the refrigerant to the power element.
The structure of such conventional expansion valve is shown in FIG. 9 and FIG. 10. FIG. 9 is a schematic view showing the external structure of the expansion valve, and FIG. 10 is a cross-sectional view showing the cross-section A-Axe2x80x2 of FIG. 9 observed from the direction of the arrow. In FIGS. 9 and 10, the valve body 30 is equipped with a first passage 32 formed from the refrigerant exit of a condenser 5 via a receiver 6 to the refrigerant entrance of an evaporator 8, and a second passage 34 formed between the refrigerant exit of the evaporator 8 and the refrigerant entrance of a compressor 4, the two passages separately positioned one above the other. The passages constitute a refrigerant piping 11 of the refrigeration cycle. The first passage 32 is equipped with a valve hole 23 for performing adiabatic expansion of the liquid-phase refrigerant supplied from the refrigerant exit of the receiver 6 through the opening 321. The center line of the valve hole 23 is positioned along the longitudinal direction of the valve body 30. A valve seat is formed to the entrance of the valve hole 23, toward which a ball-shaped valve means 42 is biased by a spring 32 such as a compression coil spring via a valve support member 31.
The first passage 32 to which the liquid-phase refrigerant from receiver 6 enters functions as a liquid-phase refrigerant passage, equipped with an exit port 322, an entrance port 321, and a valve chamber 20 communicated to the entrance port 321. After expansion, the refrigerant flows out through the exit port 322 to the evaporator 8. The valve chamber 20 is a chamber with a bottom formed coaxial to the center line of the valve hole 23, which is sealed by a plug 34. A sealing member 36 is equipped to the plug 34.
A power element 50 for driving the valve member 42 is equipped to the upper end of the valve body 30. The power element 50 comprises a case 56, the interior space of which is divided by a diaphragm 54 into upper and lower pressure chambers. The lower pressure chamber 55 is communicated to the second passage 34 through a pressure equalizing hole 36e formed coaxial to the center line of the valve hole 32a. 
The second passage 34 comprises an entrance port 342 and an exit port 341, where refrigerant vapor exiting the refrigerant exit of the evaporator 8 flows in through the entrance port 342 and exits through the exit port 341 toward the compressor 4. Passage 34 functions as a passage for the gas-phase refrigerant, and the pressure of the refrigerant vapor is loaded to the lower pressure chamber 55, via the pressure equalizing hole 36e. An operating shaft 40 extending from the lower surface of the diaphragm 54 to the valve hole 23 of the first passage 32 is coaxially positioned within the pressure equalizing hole 36e. A stopper 52 is equipped to the operating shaft 40, which is placed within the lower pressure chamber 55, and contacted to the lower surface of the diaphragm 54. The operating shaft 40 is supported by the inner surface of the lower pressure chamber 55 constituting the power element 50 and the separation wall between the first passage 32 and the second passage 34 of the valve body 30 so as to slide freely in the vertical direction. The lower end of the operating shaft 40 is contacted to the valve means 42. A sealing member 44 that prevents refrigerant from leaking between the first passage 32 and the second passage 34 is equipped to the peripheral surface of the operating shaft 40 corresponding to the operating shaft slide-guide hole in the separation wall.
A known heat sensing gas for driving the diaphragm is filled in the upper pressure chamber 55. The heat of the refrigerant vapor exiting through the refrigerant exit of the evaporator 8 and traveling in the second passage 34 is transmitted to the diaphragm drive fluid through the diaphragm 54 and the valve means drive shaft 36f exposed to the second passage 34 and the pressure equalizing hole 36e communicated to the second passage 34. Further, reference number 58 shows a plug body for sealing the heat sensing gas.
The heat sensing gas inside the upper pressure chamber 55 loads the pressure corresponding to the heat transmitted thereto to the upper surface of the diaphragm 54. The diaphragm 54 is vertically displaced corresponding to the difference in the pressure between the diaphragm drive gas loaded to the upper surface thereof and the pressure loaded to the lower surface of the diaphragm 54. The vertical displacement of the diaphragm 54 drives the valve means 42 via the operation shaft 40 closer to or away from the valve seat of the valve hole 23. As a result, the flow rate of the refrigerant is controlled.
According to the above-mentioned conventional expansion valve, the valve means drive shaft 36f is positioned at the center of the valve body 30, so the power element 36 must also be positioned at the center area of the valve body 30.
Since according to the prior-art expansion valve, the pipes to which the evaporator and the compressor are connected are arranged in opposing directions, which restrict the degree of freedom when determining the mounting position of the expansion valve, the evaporator, and the compressor. Especially, when the expansion valve must be mounted in the engine room of a vehicle and the like where mounting space is limited, the mounting structure of the expansion valve becomes a problem.
The object of the present invention is to solve such problem by providing an expansion valve having an improved degree of freedom of the mounting structure.
In order to achieve the above object, the present invention provides an expansion valve for controlling the flow rate of a refrigerant provided from a compressor to an evaporator, the valve comprising a prism-shaped valve body, a passage through which the refrigerant exiting from the compressor travels, a passage through which the refrigerant returning to the compressor travels, the passages opening to a first side surface of the valve body, and a passage through which the refrigerant flowing toward the evaporator travels, a passage through which the refrigerant returning from the evaporator travels, the passages opening to a second side surface of the valve body adjacent to the first side surface equipped with the openings for the two former-mentioned passages.
A preferable example of the expansion valve according to the present invention characterizes in that a power element is mounted at a biased position against the valve body.
Moreover, the expansion valve according to the present invention is equipped with a stud bolt equipped to the first side surface of the valve body utilized for fixing the expansion valve, and two penetrating holes penetrating through the second side surface and the side surface opposite to the second side surface utilized also for fixing.
The expansion valve according to the present invention having the above-explained structure includes refrigerant passages opening to the adjacent (neighboring) side surfaces of the valve body, which enables to improve the degree of freedom of the mounting structure. Moreover, since the mounting position of the power element is biased against the valve body, the interference that may exist between the stud bolt and the penetrating holes according to the conventional structure is prevented.